Polysulfide sealants and adhesives are based on polysulfide liquid polymers which can be formulated to a one component or two component room temperature rubber curing system. In 1927, a chemist was trying to synthesize anti-freeze and discovered a gummy-like mass which would not dissolve. From this beginning, the technology advanced to provide the first liquid room temperature curing elastomeric polymer known as LP polymer. These liquid polysulfide polymers have been in use in sealants and adhesives since the 1940s. The primary function of a sealant is to seal, with load-bearing properties being secondary. The primary function of an adhesive is the transfer of load-bearing properties between two or more substrates. Today, the worldwide polysulfide sealant/adhesive market uses 30-40 million pounds of LP polymer with growth expected at 3-5% per year.
Polysulfide sealants are used in any application in which an environment is to be isolated from external or internal factors and load-bearing properties as desired. These applications include aircraft fuel cell, pressure cabin sealers, flight decks, electrical potting, window assemblies, gaskets, seams, joints, and dams when adhering to metal, wood, concrete or composite material.
Polysulfide sealants are important due to their excellent fuel resistance, low-temperature flexibility and adhesion to a variety of surfaces. In addition, acceptable UV, moisture, and electrical resistance is present with good vibration-damping properties.
Polysulfide sealants exhibit these properties at low costs depending on the application. In the aerospace industry, polysulfide sealants are the most cost-effective means of sealing an aircraft.
Despite the long history of the use of polysulfides there is still a need for providing improved sealants especially with regard to corrosion inhibition where, for environmental concerns, nonchromated corrosion inhibitors are required.
Vapor phase corrosion-inhibiting compositions are described in U.S. Pat. Nos. 5,139,700; 5,209,869; 5,344,589; and 5,320,778. Mixtures of organic and inorganic salts form part of the composition with polyolefins. Phosphosilicates are not mentioned.
Corrosion-inhibiting compositions are described as part of lubricants in the fuel industry in U.S. Pat. Nos. 4,612,129; 5,338,537; 5,403,501; and 5,407,471. None of the patents describe the particular combination of a phosphosilicate and organic and inorganic salts.
Corrosion-inhibiting components are admixed with polyurethanes to form coatings as described in U.S. Pat. Nos. 5,124,385 and 5,236,983. These do not describe the particular combination of corrosion-inhibiting ingredients employed in the present invention.